This application claims the priority of German Application No. 100 15 514.6 filed Mar. 30, 2000, which is incorporated herein by reference.
This invention relates to a fin-stabilized projectile having fins mounted at the rear portion of the projectile and pivotal about respective rotary axes oriented transversely to the longitudinal projectile axis.
In a known projectile of the above type, described, for example in German patent document 34 08 585, the fins movably supported in the rear portion of the projectile can unfold exclusively under the effect of centrifugal forces generated during spin of the projectile, for moving the fins into their effective, deployed position to stabilize the projectile. Deploying fins in this manner, however, is not possible in projectiles which do not spin during flight, such as artillery projectiles where torque transmission from the barrel rifling to the projectile is prevented by a guide band which rotates relative to the projectile.
Also disadvantageously, in the known projectile the fins project in their folded state beyond the rearward end of the projectile. Therefore, such a projectile cannot be used in artillery systems in which predetermined barrel lengths or volumes and thus predetermined interfaces have to be observed for the projectile, on the one hand and, for example, for the propellant, on the other hand. By virtue of the fact that in such a prior art projectile the air pressure point cannot be altered with respect to the center of gravity of the projectile, no sufficient improvement of the flight stability is possible. It is a further disadvantage that the known fin arrangement provides no space for a payload.
It is an object of the invention to provide an improved deployable guide assembly for stabilizing a substantially non-spinning artillery projectile in such a manner that in the folded state of the guide assembly the projectile volume is not exceeded with respect to predetermined interfaces, but nevertheless, an improvement of the aerodynamic properties is achieved in the deployed state of the guide assembly.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the fin-stabilized projectile includes a projectile body having a rear portion defining a rearwardly open cavity and a stabilizing assembly which has a fin support accommodated in the cavity and is axially slidable relative thereto. The fin support has a withdrawn position in which the fin support is substantially retracted into the cavity and an axially outwardly shifted position in which the fin support projects rearward and outwardly from the projectile body. A plurality of fins are held in the fin support for pivotal motion about an axis transverse to the longitudinal projectile axis. Each fin has a folded state in which it is retracted in the fin support when the latter is in the withdrawn position and a deployed state in which it is unfolded and extends substantially externally of the fin support when the latter is in its outwardly shifted position. Arrangements are provided which axially displace the fin support when the projectile has left the weapon barrel after firing and which move the fins into the deployed state when the fin support assumes its outwardly shifted position.
The invention is based on the basic principle to arrange the fins in a fin support which is located at the rear portion of the projectile and which is axially rearwardly slidable, whereby a significant improvement of the flight stability is achieved by a rearward relocation of the air pressure point at the guide assembly with respect to the approximately constant center of gravity of the projectile.
Further, the invention provides that after the projectile has left the weapon barrel, the fins may, in the axially displaced position of the fin support, unfold automatically into the deployed end position without needing centrifugal forces therefor.
Advantageously, the axial displacement of the fin support is effected by directing the propellant gases through apertures, provided in the fin support, into a chamber which is situated in the projectile in front of the fin support. Thus, in the chamber approximately the same pressure prevails as behind the projectile during its travel within the weapon barrel. A higher pressure in the chamber will develop only as the projectile leaves the weapon barrel and thus a pressure drop externally of the weapon barrel occurs. As a result, the higher pressure in the chamber shifts the fin support axially rearward, partially out of the projectile body. Thereafter a respective compression spring positioned at each two-part fin effects an automatic deployment of the fins from a space-saving folded, initial position within the projectile into an outward telescoping, deployed, operating position in which the fin length is doubled compared to its folded state. Such a deployment step is further advantageously achieved in a first phase by obliquely configured fin edges gliding on corresponding oblique slide faces provided on the fin support and in a second phase by the forces derived from the air flow and acting on the fins.
In addition to the above-described significant improvement of the flight stability, the invention further makes possible, due to the space-saving arrangement of the fins, the accommodation of a substantial payload, such as a base-bleed assembly.